1. Field Of The Invention
This invention relates generally to a fluid absorbent article and to a method for absorbing fluids, such as pus, urine or menstrual fluids, in a corporeal environment.
2. Description Of The Related Art
In the field of absorbent articles, there has been an ongoing effort to provide improved articles of the type comprising an absorbent web joined to a topsheet, for use in applications such as disposable diapers, sanitary napkins, incontinence pads, and the like, whereby fluids may quickly and efficiently be sorbed. A specific problem associated with numerous absorbent articles developed to date for such applications involves flow-back of previously sorbed fluid from the absorbent web. Considering a disposable diaper as an illustration, when a baby sits or moves while wearing the diaper, significant pressure is exerted on portions of the absorbent web and causes the exudation of previously sorbed fluid therefrom, whereby the fluid may be brought in contact with the baby's skin, resulting in excessive skin wetness, diaper rash, infection of scratches or lacerations in the diaper wearing area, etc. Accordingly, a variety of designs and configurations of absorbent articles has been proposed and/or employed in the prior art to overcome such problem, so that the topsheet associated with the absorbent web is kept dry in use, consistent with retention of the sorbed fluid in the absorbent web, despite pressure or deforming forces exerted thereon.
U.S. Pat. Nos. 3,814,101 and 3,886,941 issued to T. F. Kozak and J. J. Duane, et al., respectively, disclose a disposable absorbent article useful in diapers, incontinence pads and the like, which is said to readily permit flow of liquid in the direction of the absorbent layer through the topsheet associated therewith, but which substantially reduces the possibility of flow in the opposite direction. The topsheet may be formed from a non-fibrous hydrophobic material such as thermoplastic film, and features a plurality of valvular apertures therein. These valvular openings may be of two basic types, substantially straight slits and punctures. An array of dimple depressions is situated across the surface of the topsheet. The patent states that the configuration of these dimples can be circular, elliptical, rectangular, diamond-shaped, and the like, the important criteria being that they are formed so that there is substantially no breaking or cutting of the topsheet during or after fabrication. The slits are disclosed as being from about 0.030 to about 0.25 inch in length, at a density of from about 30 to about 150 slits per square inch.
The dimples in the above-described system extend below the plane of the topsheet a short distance, so that the absorbent material immediately below the dimples is in a compressed state. The arrays of respective slits and dimples intersect so that where a dimple is formed over a portion of a slit, the slit is stated to be open to a much greater degree than the corresponding slits situated remote from the dimples on the topsheet's surface. Likewise, the slits disposed between corresponding dimples are said to be open to a greater extent than would be the case if no dimples were present. In use, as liquid is transferred to the absorbent pad through the slits, the absorbent pad absorbs the liquid through its entire area until either partial or full saturation is achieved. The compressed material expands during the sorption and urges the dimples upward, closer to the plane of the topsheet. This action serves to close the previously opened slits, thereby trapping the liquid in the absorbent pad. As a general rule, it is stated that the total area occupied by the dimples should not occupy more than about 20% of the area of the absorbent material. The patent indicates that the absorption of liquid is accomplished through the valvular slits as contrasted to absorption through the thermoplastic topsheet in the non-ruptured depressed areas.
U.S. Pat. No. 3,888,256 to H. Studinger describes a multilayer absorbent pad, wherein an upper layer is a plastics-bound fibre fleece or web, beneath which there is disposed at least one layer of cellucotton acting as a filter layer and preventing the underlying material from escaping from the absorbent pad. Beneath the layer(s) of cellucotton there is disposed at least one layer of a swelling substance which may be powdery or granular in form and consists of polyacrylamide, sulphonated polystyrene or other suitable substance, which may be fixed, e.g., adhered, to a carrier sheet of cellucotton. Beneath the layer of sewlling substance there is disposed a relatively thick layer which may be one or more layers of cellulose wadding. Crepe paper or cellucotton may be utilized in this layer in place of cellulose wadding. Finally, there is disposed a bottom layer which may also consist of at least one surface layer of cellucotton, plastics-bound fibre fleece or liquid-impervious foil, such as polyethylene foil. In operation, liquid impinging on the upper surface layer of the pad will penetrate thereinto and leak into the absorbent layer of cellulose wadding, crepe paper or cellucotton. Resulting contact of the liquid with the swelling substance layer causes the particles therein to swell and coalesce into a jellylike liquid impervious layer, creating a barrier for the liquid already present in the absorbent layer. Subsequent squeezing or pressure imposed on the absorbent pad will not result in expression of liquid out of the absorbent layer, so that the article remains dry even if subjected to violent treatment resulting in considerable surface deformation of the pad.
U.S. Pat. No. 4,429,001 to E. E. Koltin, et al discloses absorbent sheets prepared from a coherent web of entangled blown fibers formed by extruding liquid fiber-forming material into a high-velocity gas stream. An array of superabsorbent polymeric particles is dispersed within the web. Sheet products of such materials will expand greatly in size during sorption, the constituent fibers typically increasing in thickness by a factor of 10. The fibers employed in this nonwoven matrix may be derived from polypropylene, polyethylene, polyethylene terephthalate, and polyamides. These materials are disclosed to be suitable for forming meltblown fibers. Alternatively, the fibers may be formed by solution blowing, from materials such as polymers or copolymers of vinyl acetate, vinyl chloride, and vinylidene fluoride. Inorganic materials also are disclosed as suitable for forming the fibers. The absorbent materials in the matrix may comprise modified starches, and high molecular weight acrylic polymers containing hydrophilic groups. For liquids other than water, alkylstyrene absorbent particles may be employed.
U.S. Pat. No. 3,929,135 H. A. Thompson, discloses an absorptive article suitable for applications such as diapers, sanitary napkins, incontinence pads, and the like, comprising a fluid-impervious topsheet material provided with tapered capillaries, each of which has a base in the plane of the topsheet and an apex remote from the plane, the apex being in intimate contact with an absorbent element. The angle of taper of the capillaries is from about 10.degree. to about 60.degree., the base opening dimension is from about 0.006 to about 0.250 inch, and the apex opening dimension is from about 0.004 to about 0.100 inch. Such topsheet is alleged to allow the free transfer of fluids from the body contiguous thereto, into the absorbent element of the device while inhibiting the reverse flow of these fluids. The topsheet is constructed of a liquid impervious material such as low density polyethylene at a thickness of 0.001-0.002 inch. The capillaries may be in the form of a frustum of a conical surface, pyramid or similar body with a triangular, square or polygonal base; additionally, they may be asymmetric, and the angle of taper may change continuously from the base to the apex thereof. Capillaries also may be provided in the form of slots having sides and ends tapered at angles analogous to circular capillaries. Capillary base diameters must be small enough to allow a liquid droplet to bridge across at least one capillary. The patent states at column 4, lines 50-52 that the height of the tapered capillary should provide a structure wtih a minimum tendency to collapse in use. The criterion that no reverse flow of fluid occurs in the absorbent element when same is placed under pressure, is achieved by having the absorbent element constructed so that less than the full saturation level is reached in use. In other words, the absorbent element is designed and constructed to contain a significantly larger quantity of fluid than is anticipated that the device will be required to contain in a practical use situation. The absorbent pad may comprise any suitable absorbent material such as comminuted wood pulp (airfelt), crepe cellulose wadding, etc.
The prior art thus has proposed a variety of absorptive structures and absorbent articles for applications such as sanitary napkins, disposable diapers and the like. However, all of the aforementioned prior art teachings are characterizable by deficiencies in fabrication and/or in use, insofar as the objective is concerned with providing a sorbent article which sorbs fluid to keep a topsheet or upper layer of the article dry. For example, the absorbent articles disclosed in the aforementioned U.S. Pat. Nos. 3,814,101 and 3,886,941, comprising a plurality of valvular aperatures and a system of dimples disposed across the surface of a topsheet, represent a comparatively complex structure insofar as the topsheet fabrication and processing steps are concerned. The five-layered composite of U.S. Pat. No. 3,888,256 is complex in terms of its many constituent elements, and thus is likely to have a high production cost. The sorbent sheet product of U.S. Pat. No. 4,429,001 does not disclose an application to any structure which will provide a dry topsheet surface. The absorptive article of U.S. Pat. No. 3,929,135 represents a generally efficient structure insofar as the topsheet is concerned, however in meeting the objective of effectively inhibiting the reverse flow of fluids from the absorbent element, the article must, as disclosed, provide an excess of the absorbent so that its sorptive capacity is not exceeded. Accordingly, the provision of absorbent in such system must be subject to a large safety factor, insofar as the amount of sorbent material is concerned, to assure that even under high fluid loading conditions in use, the absorbent is not so saturated as to exclude fluid when placed under pressure, such as where an infant is sitting or moving about in a wet disposable diaper.
Accordingly, it is an object of the present invention to provide an improved fluid absorbent article, of the type wherein a topsheet is joined to an absorbent material.
It is another object of the present invention to provide a fluid absorbent article of such type, which is comparatively simple in construction and of low fabricational cost.
It is a further object of the present invention to provide a fluid absorbent article wherein a minimum quantity of absorbent material is necessary.
Other objects and advantages of the present invention will be apparent from the ensuing disclosure and appended claims.